1. Field of the Invention
The present invention relates to a fingerprint image acquisition apparatus and method thereof, and more particularly, to a fingerprint image acquisition apparatus and method thereof which can acquire a fingerprint image by dividing the region of ridges having narrow interval, when acquiring the fingerprint image formed on the finger, by using a contacting type fingerprint image acquisition apparatus.
2. Description of the Related Art
As a personal computer and a communication network supplies rapidly, there increased the requirements of identification procedures in person in various fields, such as an authorization and permission in public office, an entrance and exit control of special region in which the preservation of public peace is required, an electronic commerce by using a credit card, receipt of money and drawing in a bank. In the procedure of confirming one's identity, although a security system using security devices such as a key, an ID card, and a secret number etc. is used, it has several problems that the key, ID card, and the secret number is easy to make a copy or likely to lose.
To prevent the above security devices from copying or losing, recently, a living body measurement security apparatus has been developed and supplied. In the living body measurement security apparatus, the one's identity is confirmed by using various living bodies such as a fingerprint, palm, eyes, face and voice etc. as the unique body character of human. Accordingly, it is prevented the accidents caused by copying or losing the several security devices originally.
Hereinafter, as a conventional method for confirming one's identity, the method for acquiring a fingerprint formed on a finger will be described. FIG. 1 is a side view illustrating a fingerprint image acquisition apparatus in accordance with the conventional art. FIG. 2 is a view illustrating a dividing state of a fingerprint image generated from the fingerprint image acquisition apparatus shown in FIG. 1. As shown in FIGS. 1 and 2, the fingerprint image acquisition apparatus 1 comprises a fingerprint sensing device unit 2, a lens 3 and a CCD (Charge Coupled Device) device unit 4. Here, the fingerprint sensing device unit 2 changes the image of ridge and valley of a fingerprint fp, formed on a finger f, when contacting the finger f with it, into a photo signal and then outputs. Accordingly, all devices capable of performing the above function can be adapted to the fingerprint sensing device unit 2.
More in detail, when a user's finger is contacted with the fingerprint sensing device unit 2 with a predetermined pressing pressure, the fingerprint sensing device unit 2 changes the formation of the fingerprint fp formed on the finger into a photo signal and then generates.
The photo signal generated from the fingerprint sensing device unit 2 is transmitted to the CCD device unit 4 through the lens 3. The lens 3 controls the photo signal to be focused on a surface of the CCD device unit 4. The CCD device unit 4 changes the irradiated photo signal into an electrical signal and then outputs it, thereby outputting a fingerprint image. The fingerprint image outputted from the CCD device unit is stored to a video memory (not shown). The gray level of the fingerprint image, which is stored to the video memory, is divided as 256 levels. Among those, gray levels of 0 to 5 are noises and only gray levels of 60% above are acquired and stored to the video memory.
When storing the fingerprint image to the video memory, the fingerprint image acquired from the CCD device unit 4 is stored by dividing it into a plurality of unit block B as shown in FIG. 2. FIG. 3 is a view illustrating a fingerprint image stored to the video memory. As shown in FIG. 2, a fingerprint image is divided into the size of 8×6, thereby acquiring 48 unit blocks B. To acquire more precise image, the fingerprint image outputted from the CCD device unit is divided into the size of 192×192 and stored. Thereafter, the image stored to the video memory is compared to a previously stored fingerprint image, thereby confirming one's identity.
As described above, the conventional fingerprint image acquisition method has a problem that when the fingerprint image is acquired by dividing it into unit blocks with a constant size regardless of the width of ridges of the fingerprint formed on a finger, as shown in FIG. 3, the fingerprint image acquisition states become different at a region having narrow interval between the ridges and at another regions, especially, a clear fingerprint image can not obtained at the region having narrow interval between the ridges.